Inversion in the temperature coefficient of the optical path length close to the glass transition temperature in tellurite glasses

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Tissue response to experimental dental cements prepared from a modified power glass composition

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Thermal-optical properties of Ga : La : S glasses measured by thermal lens technique

In this work the quantitative theoretical treatment for two beam mode mismatched thermal lens spectrometry is applied to investigate the thermo-optical properties of chalcohalide (chalcolgenides and halides mixture) glasses. For the three kinds of glass studied the thermal diffusivity varied between 2.5 and 2.7 x 10(-3) cm(2) s(-1). Using these results and supposing Dulong-Petit specific heats we estimated the thermal conductivity and temperature ratio of optical path length (ds/dT) and temperature coefficient of refractive index (dn/dT). All samples had positive ds/dT(similar to 3.3 x 10(-6) K-1) and negative dn/dT (similar to -26 x 10(-6) K-1). The difference between these parameters and the change of signal are consequences of the expansion coefficient (13 x 10(-6) K-1) and refractive index (n similar to 2.6) of chalcohalides. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Thermal properties of fluoride glasses and their gel precursors

Xerogels were prepared from zirconium, barium, aluminum, lanthanum and lithium acetates, corresponding to a Li containing ZBLA composition. The study of their thermal properties (DSC, TG/DTG, FT-IR) showed that they might be used as chemically stable precursors in the preparation of fluoride glasses. Hydrofluoric acid in solution was chosen as a mild fluorinating agent. This newly proposed technique of fluorinating allowed to obtain high quality ZBLALi glass which presents the advantage of higher thermal stability and homogeneity in comparison with the glass obtained using individual commercial fluorides.

Methods to estimate the number of surface nucleation sites on glass particles

Based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory, we propose two new models to describe the crystallisation kinetics of glass particles and use them to determine the density of nucleation sites, N(s), on glass powders. We tested these models with sintered compacts of diopside glass particles using sinter-crystallisation treatments at 825 degrees C (T(g)similar to 727 degrees C), that covered from null to almost 100% crystallised volume time fraction. We measured and compared the evolution of the crystallised volume fractions by optical microscopy and x-ray diffraction. Then we fit our expressions to experimental data using Ns and R (the average particle radius) as adjustable parameters. For comparison, we also fit to our data existing expressions that describe the crystallised volume fraction in glass powders. We demonstrate that all the methods allow one to estimate N(s) with reasonable accuracy. For our ground and water washed diopside glass powder, N(s) is between 10(10)-10(11) sites.m(-2). The reasonable agreement between experimental and adjusted R confirms the consistency of all five models tested. However, one of our equations does not require taking into account the change of crystallisation mode from 3-dimensional to 1-dimensional, and this is advantageous.

Defect-induced photoluminescence of powdered silica glass

Visible photoluminescence was generated in standard soda-lime-silica glass powder, mechanically milled in a high-energy attrition mill. The broad emission band maximum shows a linear dependence on the exciting wavelength, suggesting the possibility to tune the PL emission. The photoluminescence was attributed to defect generation related to unsatisfied chemical bonds due to the high surface area. Raman scattering and ultraviolet-visible optical reflectance measurements corroborate this assertion. Transmission electron microscopy measurements indicate that the powder is composed by nanocrystallites with about 10-20 nanometers immersed in an amorphous media.

Analysis of curaua/glass hybrid interlayer laminates

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caracterização de argilas usadas para produção de cerâmica vermelha e estudo das alterações nas suas propriedades pela adição de resíduos

Neste trabalho são apresentados os resultados de caracterização das principais argilas usadas pela indústria cerâmica vermelha regional e, também, de alguns resíduos sólidos produzidos na região de Presidente Prudente - SP. Os resultados da incorporação destes resíduos em massas cerâmicas são avaliados através do estudo de suas propriedades tecnológicas. Para a caracterização dos materiais foram utilizadas as seguintes técnicas: análise textural (concentração das frações areia, silte e argila), difratometria de raios X e análise térmica. As propriedades tecnológicas de corpos de prova cerâmicos foram avaliadas através dos seguintes parâmetros: retração linear (RL), perda de massa ao fogo (PF), massa específica aparente (MEA), porosidade aparente (PA), absorção de água (AA) e resistência mecânica à flexão (RMF). Corpos de prova, com diferentes concentrações de resíduos, foram prensados (prensa uniaxial manual) e queimados em temperaturas que variaram de 800 a 1200 oC, usando um forno tipo mufla com controle de temperatura. As argilas sedimentares foram coletadas nas margens do rio Paraná e em áreas de várzea, próximas as cerâmicas. As amostras estudadas, coletadas nos depósitos das cerâmicas, são usadas para produção de tijolos maciços, blocos furados e telhas. Quatro tipos diferentes de resíduos foram estudados: (1) lodo de estação de tratamento de água ETA, (2) torta de filtro de indústria de re-refino de óleo lubrificante, (3) pó de vidro (soda-cal) de garrafa tipo long neck descartável, e (4) cinza de bagaço de cana. Estes resíduos foram incorporados em massas cerâmicas coletadas nas indústrias... (Resumo completo, clicar acesso eletrônico abaixo)

Electrical conductivity of Ag-Na ion exchanged soda-lime glass

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Proposta para melhoria da qualidade dos produtos cerâmicos e de criação de um polo cerâmico artesanal na cidade de Indiana - SP

This work presents a proposal to create a Polo Ceramic Craft in the town of Indiana - SP, through the potter’s organization in a cooperative that will coordinate activities to add value to ceramic pieces. To achieve this, two things are essential: improving the ceramic body and improve the properties of the ceramic material. For the first action it’s necessary to create a Central Mass Production of Ceramics, to provide raw materials and homogeneous composition that results in differentiated ceramic after burning process (sintering). To this end, we propose the incorporation of additives (which act as fluxes) to the clay material. These additives can be mineral such as feldspar and nefelinas or leavings, such as glass powder obtained from disposable containers. For the second action is necessary to acquire an oven, electric or gas, it reaches higher temperatures (around 1200 ° C). The presence of the additive and burning at higher temperatures will enable better production of sintered ceramic material with less porosity and water absorption and higher mechanical strength, and pieces vitrified and glazed, allowing them to assign a higher value. For the production of these materials (thinner walls) requires a smaller volume of clayey raw materials. Besides benefiting the ceramic pieces, the proposed changes reduce the environmental impact caused by burning wood, since it will be replaced by natural gas (or electricity), and even will reduce the disposal of glass containers in the environment by recycling and incorporating this material in the clay. From a social standpoint, the cooperative is crucial to the viability of the proposed project, to coordinate activities and commercial production, which will result in better wages and profits for companies and consequently for the city and its population

Recycling scrap automotive heat shield insulation material

Automotive heat shields are usually composed of two metal sheets enclosing an insulating material with a paper-like texture that contains refractory ceramic particles. This article discusses the results achieved by recycling the scrap automotive insulation that is discarded in landfills, using the same concept as paper recycling. For comparison with the original product, tests of thickness, bulk density, weight loss on ignition, tensile strength, compressibility, and recovery were performed on recycled materials produced in a so-called "manual" process (involving little automation and performed in adapted facilities) without pressing, and pressed once, twice, and four times. Materials recycled in a so-called "industrial" process (in a paper recycling plant) without pressing, and pressed once were also tested. The recycled materials can be considered approved with respect to the main requirement, thermal insulation, since they dissipated the under-hood temperature by more than 300 A degrees C (like the original product). Like the heat insulation tests, the thermogravimetric analysis suggested that the recycled materials showed higher stability than the original product. Thermogravimetric, microscopy, and energy dispersive spectroscopy analyses indicated that the structural and compositional characteristics of the original product were preserved after recycling.

Propriedades estruturais e térmicas de vidros teluretos 20Li2O-80TeO2

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Preoperative warming combined with intraoperative skin-surface warming does not avoid hypothermia caused by spinal anesthesia in patients with midazolam premedication

CONTEXTO E OBJETIVO: Hipotermia inadvertida no perioperatório é freqüente durante anestesia subaracnóidea e após a administração de midazolam. O objetivo foi avaliar os efeitos do aquecimento da pele no intra-operatório, associado ou não ao aquecimento da pele durante o período de 45 minutos no pré-operatório, na prevenção de hipotermia intra- e pós-operatória determinada pela anestesia subaracnóidea em pacientes com medicação pré-anestésica com midazolam. TIPO DE ETUDO E LOCAL: Estudo prospectivo e aleatório, realizado no Hospital das Clínicas, Universidade Estadual Paulista (Unesp), Botucatu, SP. MÉTODOS: O estudo foi realizado em 30 pacientes com estado físico ASA (da Sociedade Norte-americana de Anestesiologistas) I e II submetidos à cirurgia eletiva do abdômen. Como medicação pré-anestésica, utilizou-se o midazolam, 7,5 mg via intramuscular (IM) e anestesia subaracnóidea padrão. em 10 pacientes (Gcontrole) utilizou-se isolamento térmico passivo; 10 pacientes (Gpré+intra) foram submetidos a aquecimento ativo no pré- e intra-operatório; e 10 pacientes (Gintra) foram aquecidos ativamente somente no intra-operatório. RESULTADOS: Após 45 minutos de aquecimento no pré-operatório, os pacientes do Gpré+intra apresentaram temperatura central mais elevada em relação aos dos grupos não aquecidos antes da anestesia (p < 0,05) mas não no início da cirurgia (p > 0,05). Os pacientes que receberam aquecimento no intra-operatório apresentaram temperatura central mais elevada no final da cirurgia em relação aos de Gcontrole (p < 0,05). Todos os pacientes estavam hipotérmicos na admissão da sala de recuperação pós-anestésica (temperatura central < 36º C). CONCLUSÕES: 45 minutos de aquecimento no pré-operatório combinado com aquecimento no intra- operatório não evita, mas minimiza a ocorrência de hipotermia determinada pela anestesia subaracnóidea em pacientes que receberam midazolam como medicação pré-anestésica.

Exothermic Behavior, Degree of Conversion, and Viscoelastic Properties of Experimental and Commercially Available Hard Chairside Reline Resins

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Uso das técnicas de infravermelho e de ressonância magnética nuclear na caracterização da reação ácido-base de um cimento odontológico experimental

Glass ionomer cements (GICs) are products of the acid-base setting reaction between an finely fluoro-alumino silicate glass powder and poly(acrylic acid) in aqueous solution. The sol gel method is an adequate route of preparation of the glasses used to obtain the GICs. The objective of this paper was to compare two powders: a commercial and an experimental and to investigate the structural changes during hardening of the cements by FTIR and Al MAS NMR. These analyses showed that the experimental glass powder reacted with organic acid to form the GICs and it is a promising material to manufacture dental cements.